Dual panel pixel readout in an imager

ABSTRACT

An imager having two panels of pixels (i.e., the imager&#39;s rows of pixels are split into two panels) that are controllable by separate row decoders. The dual panel architecture allows pipelining of pixel readout and column readout operations to improve the imager&#39;s frame rate. The dual panel architecture may use a standard pixel configuration, a shared column and/or a shared row and column configuration.

FIELD OF THE INVENTION

The invention relates generally to imaging devices and more particularly to dual panel pixel readout in an imaging device.

BACKGROUND

A CMOS imager circuit includes a focal plane array of pixel cells, each one of the cells including a photosensor, for example, a photogate, photoconductor or a photodiode overlying a substrate for accumulating photo-generated charge in the underlying portion of the substrate. Each pixel cell has a readout circuit that includes at least an output field effect transistor formed in the substrate and a charge storage region formed on the substrate connected to the gate of an output transistor. The charge storage region may be constructed as a floating diffusion region. Each pixel may include at least one electronic device such as a transistor for transferring charge from the photosensor to the storage region and one device, also typically a transistor, for resetting the storage region to a predetermined charge level prior to charge transference.

In a CMOS imager, the active elements of a pixel cell perform the necessary functions of: (1) photon to charge conversion; (2) accumulation of image charge; (3) resetting the storage region to a known state before the transfer of charge to it; (4) transfer of charge to the storage region accompanied by charge amplification; (5) selection of a pixel for readout; and (6) output and amplification of a signal representing pixel charge. Photo charge may be amplified when it moves from the initial charge accumulation region to the storage region. The charge at the storage region is typically converted to a pixel output voltage by a source follower output transistor.

CMOS imagers of the type discussed above are generally known as discussed, for example, in U.S. Pat. No. 6,140,630, U.S. Pat. No. 6,376,868, U.S. Pat. No. 6,310,366, U.S. Pat. No. 6,326,652, U.S. Pat. No. 6,204,524 and U.S. Pat. No. 6,333,205, assigned to Micron Technology, Inc., which are hereby incorporated by reference in their entirety.

FIG. 1 illustrates a portion of a conventional CMOS imager 10. The illustrated imager 10 includes an array of pixels 20 connected to a column sample and hold circuit 42 by pixel output lines 32. The imager 10 also includes a row decoder and driver 40, column decoder 44, readout programmable gain amplifier (PGA) 50, an analog-to-digital converter (ADC) 55, an image processor 60 and a control circuit 70.

Under the control of the control circuit 70, row lines RL connected to a row of pixels 20 are selectively activated by the row decoder and driver 40. Each pixel 20 in the activated row outputs sequentially a reset V_(rst) and pixel signal V_(sig), not necessarily in that order, on a corresponding pixel output line 32. The column sample and hold circuit 42 samples, holds and then outputs the reset V_(rst) and pixel signals V_(sig) to the amplifier 50 as selected by the column decoder 44. A differential signal (V_(rst)-V_(sig)) is produced by the amplifier 50. The differential signal is digitized by the analog-to-digital converter 55. The analog-to-digital converter 55 supplies the digitized pixel signals to the image processor 60, which forms a digital image output.

Thus, every pixel 20 in a row is readout and input into the column sample and hold circuit 42, and then each column is serially (or sequentially) readout from the sample and hold circuit 42 for further processing. An exemplary timing diagram of the pixel readout and serial column readout is illustrated in FIG. 2. As can be seen from FIG. 2, row processing time t_(r) is equal to t_(p)+t_(cr), where t_(p) is the time to readout the reset V_(rst) and pixel signals V_(sig) from the pixel 20 and t_(cr) is the column readout time (i.e., total time to readout each column in a serial manner). An imager's frame rate (the inverse of the time required to readout an entire array) is dependent upon the row processing time t_(r). It is desirable to improve an imager's frame rate. If t_(p) is 6 μsecs and t_(cr) is 42.67 μsecs (e.g., 2048 columns @ 48 Mhz), row processing time t_(r) is 48.67 μsecs.

Accordingly, there is a desire to decrease row processing time so that an imager's frame rate can be improved.

SUMMARY

The invention provides an imager with decreased row processing time and improved frame rate.

Various exemplary embodiments of the invention provide an imager having two panels of pixels (i.e., the imager's rows of pixels are split into two panels) that are controllable by separate row decoders. The dual panel architecture allows pipelining of pixel readout and column readout operations to improve the imager's frame rate. The dual panel architecture may use a standard pixel configuration, a shared column and/or a shared row and column configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages and features of the invention will become more apparent from the detailed description of exemplary embodiments provided below with reference to the accompanying drawings in which:

FIG. 1 is a diagram of a CMOS imager;

FIG. 2 is a timing diagram of the operation of the FIG. 1 imager;

FIG. 3 is a diagram of another CMOS imager;

FIG. 4 is a timing diagram of the operation of the FIG. 3 imager;

FIG. 5 is a diagram of a CMOS imager constructed in accordance with an exemplary embodiment of the invention;

FIG. 6 is an exemplary timing diagram of the operation of the FIG. 5 imager;

FIG. 7 is a diagram of a CMOS imager constructed in accordance with another exemplary embodiment of the invention;

FIG. 8 is a diagram of a CMOS imager constructed in accordance with yet another exemplary embodiment of the invention; and

FIG. 9 shows a processor system incorporating at least one imaging device constructed in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Referring to the figures, where like reference numbers designate like elements, FIG. 3 shows an imager 110 having a shared pixel architecture. That is, two neighboring pixels 120 a, 120 b in the same row share readout circuitry such that their reset and pixel signals can be output to the same column's pixel output line 132. This is done to improve fill factor of the pixels 120 a, 120 b, but as is discussed below with respect to FIG. 4, it does not improve row processing time.

The illustrated imager 110 includes a column sample and hold circuit 142 connected to the pixel output lines 132 by multiplexers 134. Multiplexers 134 are required to ensure that the signals from each pixel 120 a, 120 b are sampled and held by appropriate circuitry within the column sample and hold circuitry 142. The imager 110 also includes a row decoder and driver 140, column decoder 144, readout programmable gain amplifier (PGA) 150, an analog-to-digital converter (ADC) 155, an image processor 160 and a control circuit 170.

Under the control of the control circuit 170, row lines RL connected to a row of pixels 120 a, 120 b are selectively and sequentially activated by the row decoder and driver 140. Each pair of pixels 120 a, 120 b in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 132 (at appropriate separate reset and pixel readout stages). The multiplexer 134 ensures that the column sample and hold circuitry 142 inputs the reset and pixel signals V_(rst), V_(sig) from the pixels 120 a, 120 b in the correct order.

The column sample and hold circuit 142, samples, holds and then outputs the reset V_(rst) and pixel signals V_(sig) to the amplifier 150 as selected by the decoder 144. A differential signal (V_(rst)−V_(sig)) is produced by the amplifier 150. The differential signal is digitized by the analog-to-digital converter 155. The analog-to-digital converter 155 supplies the digitized pixel signals to the image processor 160, which forms a digital image output.

Thus, every pair of pixels 120 a, 120 b in a row is readout and input into the column sample and hold circuit 142, and then each column is serially (or sequentially) readout from the sample and hold circuit 142 for further processing. An exemplary timing diagram of the pixel readout and serial column readout of the imager 110 is illustrated in FIG. 4. As can be seen from FIG. 4, row processing time t_(r) is equal to t_(a)+t_(b)+t_(cr), where t_(a) is the time to readout the reset V_(rst) and pixel signals V_(sig) from the first pixel 120 a, t_(b) is the time to readout the reset V_(rst) and pixel signals V_(sig) from the second pixel 120 b, and t_(cr) is the column readout time (i.e., total time to readout each column in a serial manner). If t_(a) is 6 μsecs, t_(b) is 6 μsecs and t_(cr) is 42.67 μsecs (e.g., 2048 columns @ 48 Mhz), row processing time t_(r) is 54.67 μsecs.

Thus, even though fill factor has improved, the row processing time of the imager 110 (FIG. 3) has increased, which has decreased the imager's 110 frame rate. This results from the serial readout of the first and second pixels 120 a, 120 b, followed by the serial column readout operation. It is desirable to improve the imager 110 such that it maintains its improved fill factor, yet also has improved row processing time and frame rate.

To make the imager's 110 frame rate insensitive to the increased time for pixel readout, it is proposed to pipeline the pixel readout and column readout sequences rather than having them occur serially. Existing pipelining architectures require extra sample and hold circuits per column.

This increased column complexity requires additional chip area, which is undesirable.

These architectures also contain column parallel gain circuits, which have storage capacitors at the amplifier output. In operation, after the signal is amplified, a subsequent analog-to-digital conversion step is performed. During the conversion, the sample and hold circuits prior to the gain circuits are available for reading out the next row of pixels. Thus, pipelined pixel readout with analog-to-digital conversion is possible. Unfortunately, with serial column readout and analog-to-digital conversion, the next row of pixels to be readout cannot be processed until the current sampled row is readout completely. As such, the existing pipelining architecture is not desirable.

FIG. 5 illustrates a CMOS imager 210 constructed in accordance with an exemplary embodiment of the invention. The illustrated imager 210 uses a unique configuration and pipelining to improve row processing time and frame rate without increasing column circuitry complexity and area used. The illustrated imager 210 uses a dual panel pixel array 212, consisting of a first panel 212 a and a second panel 212 b, and separate dedicated row decoders and drivers 240 a, 240 b to operate the panels in a manner that allows pixel readout and column readout to be pipelined (described below in more detail with respect to FIG. 6).

The illustrated imager 210 has a shared pixel architecture. That is, two neighboring pixels 220 a, 220 b in the same row share readout circuitry such that their reset and pixel signals can be output to the same column's pixel output line 232. This is done to improve fill factor of the pixels 220 a, 220 b. The imager 210 also includes a column sample and hold circuit 242 connected to the pixel output lines 232 by multiplexers 234. Multiplexers 234 ensure that the V_(rst), V_(sig) signals from each pixel 220 a, 220 b are sampled and held by appropriate circuitry within the column sample and hold circuitry 242. The imager 210 also includes a column decoder 244, readout programmable gain amplifier (PGA) 250, an analog-to-digital converter (ADC) 255, an image processor 260 and a control circuit 270.

The column decoder 244 generates column addresses to address the columns associated with the first panel 212 a and the second panel 212 b. The column sample and hold circuitry 242 also has separate controls for the first and second panels 212 a, 212 b.

Under the control of the control circuit 270, row lines RLa connected to a row of pixels 220 a, 220 b in the first panel 212 a are selectively activated by the first row decoder and driver 240 a. Each pair of pixels 220 a, 220 b in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 232 (at appropriate separate reset and pixel readout stages). The multiplexer 234 ensures that the column sample and hold circuitry 242 inputs the reset signal V_(rst) from the first pixel 220 a, followed by the pixel signal V_(sig) from the first pixel 220 a of the pair. The multiplexer 234 then ensures that the column sample and hold circuitry 242 inputs the reset signal V_(rst) from the second pixel 220 b, followed by the pixel signal V_(sig) from the second pixel 220 b of the pair.

Similarly, under the control of the control circuit 270, row lines RLb connected to a row of pixels 220 a, 220 b in the second panel 212 b are selectively activated by the second row decoder and driver 240 b. Each pair of pixels 220 a, 220 b in the activated row outputs its reset and pixel signals V_(rst), V_(sig) onto a corresponding pixel output line 232 (at appropriate separate reset and pixel readout stages). The multiplexer 234 ensures that the column sample and hold circuitry 242 initially inputs the reset signal V_(rst) from the first pixel 220 a, followed by the pixel signal V_(sig) from the first pixel 220 a of the pair. The multiplexer 234 then ensures that the column sample and hold circuitry 242 inputs the reset signal V_(rst) from the second pixel 220 b, followed by the pixel signal V_(sig) from the second pixel 220 b of the pair.

The column sample and hold circuit 242, samples, holds and outputs, to the amplifier 250, the reset V_(rst) and pixel signals V_(sig) from the first panel 212 a and the second panel 212 b (described below with respect to FIG. 6). A differential signal (V_(rst)−V_(sig)) is produced by the amplifier 250. The differential signal is digitized by the analog-to-digital converter 255. The analog-to-digital converter 255 supplies the digitized pixel signals to the image processor 260, which forms a digital image output.

Referring to FIG. 6, an example of the pipelined manner in which the pixel readout and column readout operations of the invention occur is now explained. When the current row ROW(N) of pixels is being readout, the second panel's pixels are readout first. Meanwhile, column readout of the stored signals from the first panel from a prior row ROW(N−1) is performed. Once the second panel's pixel signals are readout, the first panel's pixels for the current row ROW(N) are readout. At the same time, column readout of the stored signals from the second panel from the current row ROW(N) is performed. Afterwards, when pixel readout of the second panel's pixels for the next row ROW(N+1) is being performed, column readout of the stored signals from the first panel for ROW(N) is performed. Thus, as can be seen from FIG. 6, the row processing time t_(r) has been reduced to the column readout time t_(cr), which is a vast improvement over other imagers row processing times. If t_(cr) is 42.67 μsecs (e.g., 2048 columns @ 48 Mhz), row processing time t_(r) is 42.67 μsecs. This reduced row processing time t_(r) yields an improved frame rate for the imager 210 of the invention.

FIG. 7 is a diagram of a CMOS imager 310 constructed in accordance with another exemplary embodiment of the invention. The illustrated imager 310 uses the unique dual panel array 312 configuration and pipelining to improve row processing time and frame rate without increasing column circuitry complexity and area used. The illustrated imager 310 uses a dual panel array 312, consisting of a first panel 312 a and a second panel 312 b, and separate dedicated row decoders and drivers 340 a, 340 b to operate the panels in a manner that allows pixel readout and column readout to be pipelined. In the illustrated embodiment, the imager 310 includes panels 312 a, 312 b using the conventional non-shared pixel configuration illustrated in FIG. 1. It should be noted that because the imager 310 uses the dual panel array 312, respective row decoders and drivers 340 a, 340 b and pipelining, the imager 310 will have improved row processing time and frame rate as illustrated in FIG. 6.

The illustrated imager 310 also includes a column sample and hold circuit 342 connected to each column of pixels 320 by pixel output lines 332. Multiplexers are not required because each column of pixels has its own output circuitry and pixel output line 332. The imager 310 also includes a column decoder 344, readout programmable gain amplifier (PGA) 350, an analog-to-digital converter (ADC) 355, an image processor 360 and a control circuit 370.

The column decoder 344 generates column addresses to address the columns associated with the first panel 312 a and the columns associated with the second panel 312 b. The column sample and hold circuitry 342 also has separate controls for the first and second panels 312 a, 312 b.

Under the control of the control circuit 370, row lines RLa connected to a row of pixels 320 in the first panel 312 a are selectively activated by the first row decoder and driver 340 a. Each pixel 320 in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 332 (at appropriate separate reset and pixel readout stages).

Under the control of the control circuit 370, row lines RLb connected to a row of pixels 320 in the second panel 312 b are selectively activated by the second row decoder and driver 340 b. Each pixel 320 in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 332 (at appropriate separate reset and pixel readout stages).

The column sample and hold circuit 342, samples, holds and outputs, to the amplifier 350, the reset V_(rst) and pixel signals V_(sig) from the first panel 312 a and the second panel 312 b as described above with respect to FIG. 6. A differential signal (V_(rst)−V_(sig)) is produced by the amplifier 350. The differential signal is digitized by the analog-to-digital converter 355. The analog-to-digital converter 355 supplies the digitized pixel signals to the image processor 360, which forms a digital image output.

FIG. 8 is a diagram of a CMOS imager 410 constructed in accordance with yet another exemplary embodiment of the invention. The illustrated imager 410 uses a unique configuration and pipelining to improve row processing time and frame rate without increasing column circuitry complexity and area used. The illustrated imager 410 uses a dual panel array 412, consisting of a first panel 412 a and a second panel 412 b, and separate dedicated row decoders and drivers 440 a, 440 b to operate the panels in a manner that allows pixel readout and column readout to be pipelined.

The illustrated imager 410 has a combined shared-row/column pixel readout architecture such as one of the architectures disclosed in application Ser. Nos. 10/721,190 and 10/721,191, also assigned to Micron Technology, Inc., the disclosures of which are hereby incorporated by reference in their entirety. That is, two neighboring pixels 420 a, 420 b in a row and two neighboring pixels 420 c, 420 d in the adjacent row share readout circuitry such that their reset and pixel signals can be output to the same column's pixel output line 432. This is done to improve fill factor of the pixels 420 a, 420 b, 420 c, 420 d. The imager 410 also includes a column sample and hold circuit 442 connected to the pixel output lines 432 by multiplexers 434. Multiplexers 434 are required to ensure that the signals from each pixel 420 a, 420 b, 420 c, 420 d are sampled and held by appropriate circuitry within the column sample and hold circuitry 442. The imager 410 also includes a column decoder 444, readout programmable gain amplifier (PGA) 450, an analog-to-digital converter (ADC) 455, an image processor 460 and a control circuit 470.

The column decoder 444 generates column addresses to address the columns associated with the first panel 412 a and the columns associated with the second panel 412 b. Similar to the other embodiments of the invention, the column sample and hold circuitry 442 also has separate controls for the first and second panels 412 a, 412 b.

Under the control of the control circuit 470, row lines RLa connected to a row of pixels 420 a, 420 b in the first panel 412 a are selectively activated by the first row decoder and driver 440 a. Each pair of pixels 420 a, 420 b in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 432 (at appropriate separate reset and pixel readout stages). Row lines RLa connected to the adjacent row of pixels 420 c, 420 d in the first panel 412 a are selectively activated by the first row decoder and driver 440 a. Each pair of pixels 420 c, 420 d, in the activated adjacent row also outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 432 (at appropriate separate reset and pixel readout stages).

Similarly, under the control of the control circuit 470, row lines RLb connected to a row of pixels 420 a, 420 b in the second panel 412 b are selectively activated by the second row decoder and driver 440 b. Each pair of pixels 420 a, 420 b in the activated row outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 432 (at appropriate separate reset and pixel readout stages). Row lines RLb connected to the adjacent row of pixels 420 c, 420 d in the second panel 412 b are selectively activated by the second row decoder and driver 440 b. Each pair of pixels 420 c, 420 d, in the activated adjacent row also outputs its reset V_(rst) and pixel signals V_(sig) onto a corresponding pixel output line 432 (at appropriate separate reset and pixel readout stages).

The column sample and hold circuit 442, samples, holds and outputs, to the amplifier 450, the reset V_(rst) and pixel signals V_(sig) from the first panel 412 a and the second panel 412 b in the pipelined manner described above with respect to FIG. 6. A differential signal (V_(rst)-V_(sig)) is produced by the amplifier 450. The differential signal is digitized by the analog-to-digital converter 455. The analog-to-digital converter 455 supplies the digitized pixel signals to the image processor 460, which forms a digital image output.

It should be noted that careful placement of the pixels in the dual panel arrays of the invention prevents the boundary between the panels from creating image artifacts (due to discontinuity between the pixels). One desirable technique is to route the metal control wires under an upper metal shield (upper metal shielding is commonly used for power routing in the pixel). Then, the gap between control lines impacts how much light strikes the panel.

The present invention has the additional benefit of reducing the loading on the row decoder/driver circuits. Reduced loading leads to faster pixel readout times. Timing to the separate row decoders and drivers can be made the same in the case that pipelined pixel readout id not desired or required.

It should be appreciated that the invention can utilize many panel configurations and is not to be limited to a dual panel construction. That is, the panels used in the invention can comprise 2, 3, 4, or more panels as deemed appropriate for the application. All that is required is that each panel be driven by its own row decoder and that the column S/H circuitry and control circuitry be configured to operate the panels as described above.

FIG. 9 shows system 900, a typical processor system modified to include an imaging device 908 constructed in accordance with an embodiment of the invention (i.e., imagers 210, 310, 410 described above). The processor-based system 900 is exemplary of a system having digital circuits that could include image sensor devices. Without being limiting, such a system could include a computer system, camera system, scanner, machine vision, vehicle navigation, video phone, surveillance system, auto focus system, star tracker system, motion detection system, image stabilization system, and data compression system.

System 900, for example a camera system, generally comprises a central processing unit (CPU) 902, such as a microprocessor, that communicates with an input/output (I/O) device 906 over a bus 904. Imaging device 908 also communicates with the CPU 902 over the bus 904. The processor-based system 900 also includes random access memory (RAM) 910, and can include removable memory 915, such as flash memory, which also communicate with the CPU 902 over the bus 904. The imaging device 908 may be combined with a processor, such as a CPU, digital signal processor, or microprocessor, with or without memory storage on a single integrated circuit or on a different chip than the processor.

It should be appreciated that other embodiments of the invention include a method of fabricating the imaging devices 210, 310, 410 illustrated in FIGS. 5, 7, and 8. For example, in one exemplary embodiment, a method of integrating an imaging device comprises fabricating an array of pixels in at least two panels and fabricating a readout circuit coupled to the panel, the readout circuit enabling pipelined readout of the panels.

The processes and devices described above illustrate preferred methods and typical devices of many that could be used and produced. The above description and drawings illustrate embodiments, which achieve the objects, features, and advantages of the present invention. However, it is not intended that the present invention be strictly limited to the above-described and illustrated embodiments. Any modification, though presently unforeseeable, of the present invention that comes within the spirit and scope of the following claims should be considered part of the present invention. 

1-35. (canceled)
 36. A method of operating an imaging device, the imaging device comprising an array of pixels comprising first and second panels, said method comprising: sampling signals corresponding to pixels of a row n of the first panel while simultaneously outputting sampled signals corresponding to row n of the second panel, and sampling signals corresponding to pixels of a row n+1 of the second panel while simultaneously outputting the sampled signals corresponding to the pixels of the row n of the first panel, wherein n is an integer.
 37. The method of claim 36, wherein sampling signals corresponding to pixels of row n of the first panel comprises: sampling and holding reset signals from the first panel; and sampling and holding pixel signals from the first panel.
 38. The method of claim 37, wherein sampling signals corresponding to pixels of row n+1 of the second panel comprises: sampling and holding reset signals from the second panel; and sampling and holding pixel signals from the second panel.
 39. The method of claim 37, wherein pixels of the first panel are organized into pairs of first panel pixels and said step of sampling signals corresponding to pixels of row n of the first panel comprises: sampling and holding reset signals from a first pixel of each pair of first panel pixels; sampling and holding reset signals from a second pixel of each pair of first panel pixels; sampling and holding pixel signals from the first pixel of each pair of first panel pixels; and sampling and holding pixel signals from the second pixel of each pair of first panel pixels.
 40. The method of claim 39, wherein pixels of the second panel are organized into pairs of second panel pixels and said step of sampling signals corresponding to pixels of row n+1 of the second panel comprises: sampling and holding reset signals from a first pixel of each pair of second panel pixels; sampling and holding reset signals from a second pixel of each pair of second panel pixels; sampling and holding pixel signals from the first pixel of each pair of second panel pixels; and sampling and holding pixel signals from the second pixel of each pair of second panel pixels.
 41. A method of operating an imaging device having an array of pixels comprising first and second panels, said method comprising: reading out and storing signals from a current row of pixels from the second panel while simultaneously outputting stored signals from a previous row of pixels from the first panel; and reading out and storing signals from the current row of pixels from the first panel while simultaneously outputting the stored signals from the current row of pixels from the second panel.
 42. The method of claim 41, further comprising reading out and storing signals from a next row of pixels from the second panel while simultaneously outputting stored signals from the current row of pixels from the first panel.
 43. The method of claim 41, wherein reading out signals from the current row of pixels from the second panel is based on row control signals received from a first row decoder connected only to the second panel.
 44. The method of claim 43, wherein reading out signals from the current row of pixels from the first panel is based on row control signals received from a second row decoder connected only to the first panel.
 45. The method of claim 41, wherein storing signals from the current row of pixels from the second panel comprises: sampling and holding reset signals from the second panel; and sampling and holding pixel signals from the second panel.
 46. The method of claim 45, wherein storing signals from the current row of pixels from the second panel comprises: sampling and holding reset signals from the first panel; and sampling and holding pixel signals from the first panel.
 47. The method of claim 41, wherein pixels of the second panel are organized into pairs of second panel pixels and said step of reading out and storing signals from the current row of pixels from the second panel comprises: sampling and holding reset signals from a first pixel of each pair of second panel pixels; sampling and holding reset signals from a second pixel of each pair of second panel pixels; sampling and holding pixels signals from the first pixel of each pair of second panel pixels; and sampling and holding reset signals from the second pixel of each pair of second panel pixels.
 48. The method of claim 41, wherein pixels of the first panel are organized into pairs of first panel pixels and said step of reading out and storing signals from the current row of pixels from the first panel comprises: sampling and holding reset signals from a first pixel of each pair of first panel pixels; sampling and holding reset signals from a second pixel of each pair of first panel pixels; sampling and holding pixels signals from the first pixel of each pair of first panel pixels; and sampling and holding reset signals from the second pixel of each pair of first panel pixels.
 49. A method of integrating an imaging device, said method comprising: fabricating an array of pixels in at least two panels; fabricating a row decoder for each panel of pixels; and fabricating sample and hold circuitry coupled to the panels, the sample and hold circuitry adapted to sample signals corresponding to pixels of a row n of a first panel while simultaneously outputting sampled signals corresponding to row n of a second panel, and sample signals corresponding to pixels of a row n+1 of the second panel while simultaneously outputting the sampled signals corresponding to the pixels of the row n of the first panel, wherein n is an integer. 